Of all the embryonal tumors, retinoblastoma (RB) presents the greatest opportunities for elucidating etiologic factors. Several forms of RB have been described, each form associated with a distinct clinical pattern: -Familial cases comprise approximately 5-10% of the total, are almost always bilateral, and offspring of such cases have a 50% risk of developing tumor; we wish to test the hypothesis that there is an increased incidence of tissue-specific neoplasms in family members of such cases. -Genetic cases are defined by the 50% probability that offspring will be affected. All familial cases are in this category, as are the approximately 30% which are bilateral and sporadic. In an unknown fraction of these cases, a small deletion of band 13q14 has been identified. We hypothesize that exposure to agents capable of causing parental germ cell mutations prior to conception is greatest for these cases compared to sporadic non-genetic cases or to controls. Banded chromosomes of all patients will be examined so that the true fraction of deletion cases may be identified and their characteristics compared to non-deletion cases. -Non-genetic cases are always unilateral and sporadic; we hypothesize that these involve exposures during gestation or in the early postnatal period to mutagens and teratogens. This case-control study will utilize approximately 300 incident cases of RB identified over a four-year period among the 29 member institutions of the Children's Cancer Study Group. Controls will be selected by the method of random digit dialing. Interviews with parents of cases and controls will be performed by telephone and information collected concerning family history and exposures of parents and probands. Quantitation of the risk associated with specific exposures will be made by contrasting cases to age-matched regional population controls.